Data from: Crop-to-wild gene flow and its fitness consequences for a wild fruit tree: towards a comprehensive conservation strategy of the wild apple in Europe

Crop-to-wild gene flow can reduce the fitness and genetic integrity of wild species. Malus sylvestris, the European crabapple fruit tree, in particular is threatened by the disappearance of its habitat and by gene flow from its domesticated relative, Malus domestica. With the aims of evaluating threats for M. sylvestris and of formulating recommendations for its conservation, we studied here, using microsatellite markers and growth experiments: i) hybridization rates in seeds and trees from a French forest and in seeds used for replanting crabapples in agrosystems and in forests, ii) the impact of the level of M. domestica ancestry on individual fitness tree, and iii) pollen dispersal abilities in relationship with crop-to-wild gene flow. We found substantial contemporary crop-to-wild gene flow in crabapple tree populations and superior fitness of hybrids compared to wild seeds and seedlings. Using paternity analyses, we showed that pollen dispersal could occur up to 4 km and decreased with tree density. The seed network furnishing the wild apple reintroduction agroforestry programs was found to suffer from poor genetic diversity, introgressions, and species misidentification. Overall, our findings indicate supported threats for the European wild apple steering us to provide precise recommendations for its conservation.

作物向野生近缘种的基因流（Crop-to-wild gene flow）可降低野生物种的适合度与遗传完整性。其中，欧洲野苹果（Malus sylvestris）尤其面临栖息地丧失以及来自其栽培近缘种栽培苹果（Malus domestica）的基因流威胁。为评估欧洲野苹果所面临的威胁并制定其保护策略，本研究借助微卫星标记（microsatellite markers）与生长实验开展了三项研究：其一，分析法国森林中的种子与植株、以及用于农艺系统与森林重植野苹果的种子的杂交率；其二，探究栽培苹果祖先组分对单株果树适合度的影响；其三，解析与作物向野生近缘种基因流相关的花粉扩散能力。研究结果显示，野苹果种群中存在显著的当代作物向野生近缘种的基因流，且杂交个体的适合度优于野生种子与实生苗。通过父本分析（paternity analyses），本研究证实花粉扩散距离可达4公里，且随植株密度升高而降低。用于野苹果再引入农林业项目的种子体系存在遗传多样性不足、基因渐渗（introgressions）以及物种误鉴等问题。综合来看，本研究结果证实了欧洲野苹果所面临的切实威胁，据此可为其保护制定精准的指导建议。